RULE 255

A #7DRL game by Mathieu Dombrock.

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What Is This?

RULE 255 is a turn-based roguelike set inside a cellular automaton; A universe governed by a single rule number that determines how every cell of reality lives or dies.

You fell into the machine. Now you must navigate its shifting geometry, become one with it's inhabitants, and find your way down through each rule.

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Goal

Find the rule gate (portal) at the bottom of each stage and step into it to ascend.

Each stage is a new world generated by a different Elementary Cellular Automaton (ECA) rule, a number from 0 to 255 that determines the pattern of floor tiles you walk on. Some rules produce open corridors, others dense mazes, others pure chaos.

Between stages you return to RULE 255, a quiet space to review your stats and prepare for the next phase.

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Controls

Movement

Key	Action
↑ ↓ ← →	Move
W A S D	Move
H J K L	Move (Vim-style)

Actions

Key	Action
6 / Z	Recover - return to RULE 255
7 / F	Focus - center camera on rule gate

Spells

Key	Spell
1 / Q / Space	Flip
2 / E	Meta Flip
3 / R	Invert Row
4 / T	Invert World
5 / G	Invert Rule

Display

Key	Action
8 / C	Randomize color palette
9 / I	Cycle HUD mode (log / stats / off)
0	Toggle CRT shader
M	Toggle audio mute

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Will

Will is your life force and your fuel. Every move costs a small amount. Every spell costs more. Running low is dangerous; running out is fatal.

Collect potions to restore Will. If things get desperate, use Recover.

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Keys & Gates

Locked gates block your path. Collect keys to open them. One key, one gate.

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Void Entities

Dark void entities roam each stage. They close in on your each turn you are near them. They drain your Will on contact.

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Spells

Spells reshape reality. Each one costs Will.

Key	Spell	Effect
1 / Q / Space	Flip	Inverts the cell under you
2 / E	Meta Flip	Inverts all cells around you
3 / R	Invert Row	Inverts your row in the world
4 / T	Invert World	Inverts the entire world
5 / G	Invert Rule	Switches to the bitwise inverse of the current rule

Use spells to carve paths, escape enemies, or just watch the world collapse and rebuild.

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RULE 255 (The Hub)

After each stage you return to the Rule 255, an open world that shows your cumulative stats:

• Steps taken
• Will gained and lost
• Keys found and spent
• Cells created and destroyed by spells
• Voids (enemies destroyed)
• Recoveries used
• Spells cast
• Unique rules visited

RULE 255 also displays a message based on how deep you've gone. After phase 15, something changes.

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Audio Engine

The game's audio engine is powered by a custom audio system built on top of Tone.js. It dynamically generates music and sound effects based on the current game state, using musical modes and row data derived from the cellular automaton.

How It Works

• Music Generation:
  The engine uses a "row" of numbers (from the automaton) to determine which notes to play. Each number in the row maps to a note in a musical scale, and the scale itself is determined by the current musical mode (Ionian, Dorian, Phrygian, etc.). This means the background music changes as the automaton's state changes, creating a generative soundtrack that reflects the world.

• Modes:
  There are seven musical modes, each giving a different mood or flavor to the music. Modes are tied to the current rule number. Changing the mode shifts the intervals in the scale, so the same row data produces different harmonies and melodies.

• Sound Effects:
  All sound effects (moving, spells, enemies, keys, etc.) are also generated using the same scale and mode system. This ensures that every sound fits musically with the current background music, and that the audio experience is always in sync with the game's logic.

This system creates a soundtrack which feels alive, reactive, and tightly integrated with the cellular automaton at the heart of the game.

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About ECA Rules

An Elementary Cellular Automaton is one of the simplest possible rule systems. A row of cells (on or off) evolves based on each cell and its two neighbours, 8 possible combinations, each mapped to a 0 or 1. That mapping is the rule number (0–255).

Rule 30 produces apparent randomness. Rule 110 is Turing-complete. Rule 255 turns everything on. Each one generates a completely different world for you to walk through.

Palindromic Rules & Strange Effects

Some ECA rules are palindromic. Meaning their binary patterns read the same forwards and backwards. In the context of the game, palindromic rules tend to produce worlds with symmetrical, predictable patterns. Movement and spell effects behave consistently, and the world often feels stable.

However, most rules are non-palindromic. These rules generate worlds that are asymmetric and can behave in unexpected ways. In non-palindromic rules, actions like flipping a row or inverting the world can have surprising results when the world is mirrored.

Other Weirdness

• Inverting the World: This operation swaps all floor and wall cells. In palindromic rules, the world may retain some symmetry, but in non-palindromic rules, the structure can become chaotic or even trap the player in isolated regions.
• Meta Flips and Row Inversions: Because the rule's output is not symmetric, flipping or inverting can create patterns that are not easily reversible, leading to strange or irreversible changes in the world.
• Emergent Behavior: Non-palindromic rules can cause the automaton to evolve in ways that are hard to predict, sometimes creating dead ends, isolated islands, or unexpected corridors.

Experimenting with these rules and transformations is part of the challenge and mystery of the game. Sometimes, the only way out is to break the world further.

ECA On Wikipedia

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Known Bugs

• will is spent on blocked moves
• goal marker is sometimes off screen after camera focus

Unknown Bugs

• ???

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Do not fear the infinite.